I would move the acer when it is dormant, thru the colder months before the buds begin to break for next years leaves. As for your Geranium, you could do it now, by cutting most of the foliage and flowers down then splitting. but keep it well watered when transplanting. It should be ok. But I usually leave my Geran's until they are fading into autumn.

The Acer should be moved in the autumn after it has lost all or most of its leaf and before the frosts. Do make sure though that the pot you choose has has enough room for sufficient root growth.
As for the Geranium, it might be a good idea to take a couple of cuttings at the same time as insurance.

I would be tempted to move the Acer now. If it is in a an unhappy position and you are moving it to a better one then that would be better than waiting. You might lose the leaves but we are a 4-6 weeks from that happening anyway! Acers in unhappy positions die quite suddenly so improving its position might be saving it. Just make sure the pot is larger than the root ball and add in bonemeal for root development and nutrients and that you add some drainage as they hate roots sitting in compacted wet soil.

May I just ask and please dont take this the wrong way I am interested in your answers as usually on GOY questions the advise seems to be, to to move from pot to garden?

thanks everyone,will take your advice